In the offshore oil and gas industry, large floating vessels, such as a floating production, storage and offloading (FPSO) vessel or a floating storage and offloading (FSO) vessels, are used to receive produced hydrocarbons from subsea wells or manifolds or from nearby platforms or other subsea equipment, process them (in the case of an FPSO vessel), and store them until the oil and/or gas can be offloaded onto a tanker or other equipment. The FPSO/FSO vessel can be moored using a turret mooring system in which a fixed turret column is held by an internal or external vessel structure using a bearing arrangement. The vessel-bound components can weathervane freely around the turret, which is fixed via a number of anchor lines with respect to the seabed. This arrangement allows the FSO/FPSO vessel to adopt the direction of least resistance against waves, wind, and currents.
A turret-moored FPSO/FSO vessel makes use of swivels to allow for the transfer of fluids across the rotary-turret interface while the vessel weathervanes around the turret. Conventional, large diameter swivels have been limited in their pressure capacity i.e. the pressure differential or difference between pressures of the process fluid and the ambient environment up to a maximum of about 600 bars. It is desirable to provide swivel systems that can be used with higher pressure process fluids.